Radar tracking demonstrating and training instrument



H. P. BIRMINGHAM Jam 15, 1957 RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT Filed May l1, 1951 9 Sheets-Sheet 1 Jan. 15, i957 H. P. BIRMINGHAM ,777,214

RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT Filed May l1, 1951 9 She'etS-Sheet 2 lu L AA1r:

off

ATTORNEYS Jan. l5, 1957 H. P. BlRMlNGHAM RADAR TRACKING DEMONSTRATING ANDv TRAINING INSTRUMENT 9 Sheets-Sheet 3 Filed May 1l, 1951 m JNVENTUR. L HENRY l? BIRMINGHAM ,4f/Q @M BAY E www ATTORNEYS EAI) GM MMN m w r S m .mmm EN MMM.

. www bmw @hummm .mSmm mws FIG. 4

Jan. 15, 1957 H. P. BIRMINGHAM 2,777,214

RADAR TRACKING DEMONSTRATING AND 'TRAINING INSTRUMENT F iled May 1l, 1951 9 Sheets-Sheet 4 AMPL /FER 300 Zmeg INVENTOR. HENRY P. BIRMINGHAM n: BY

ATTORNEYS Jan. l5, 1957 H. P. BIRMINGHAM 2,777,214

RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT ATTORNEYS Jan 15, 1957 H. P. BIRMINGHAM 2,777,214

RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT meg - INVENTOR. HENRY P. BIRMINGHAM BY [GAD/MMM? ATTORNEYS Jan. 15, 1957 H. P. BIRMxNGHAM RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT 9 Sheets-Sheet '7 Filed May l1, 1951 NEW@ No@ .obb

k @Fm INVENTOR.

HENRY n a/RM/NGHAM (1Q M4@ "BY (f4/Mmm NGI VNW

mm E v ATTORNEYS Jan. l5, 1957 H. P. BIRMINGHAM RADAR TRACKING DEMONSTRATTNG AND TRAINING XNSTRUMENT Filed May l1, 1951 9 Sheets-Sheet 8 QOH @bk SFSFMQ kmh .Q5

ATTORNEYS Jan. 15, 1957 H. P. BIRMINGHAM 2,777,214

RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT Filed May 1l, 1951 9 Sheets--Sheet 9 67u 8*(3) #G+-#wfg r 1- -a- DIRECTOR OURSE UlV/T RADAR TRACKING DEMONSTRATING AND TRAINING INSTRUMENT Henry P. Birmingham, Washington, D. C., assigner, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application May 11, 1951, Serial No. 225,768

3 Claims. (Cl. 35-10.4)

The present invention relates generally to an instrument for training personnel in the art of radar tracking and for demonstrating the operation of radar tracking instruments. The present instrument is so designed as to closely simulate the operation of an actual train-elevation tracking radarscope, both in the results obtained therefrom and in the operation thereof.

In its general aspects, the instrument comprising the present invention is designed to operate in conjunction with a cathode ray tube whose screen is kcaused to simulate functionally the screen of an actual train-elevation tracking radarscope. A target tracking circuit is provided which enables a trainee to track an imaginary target pursuing an imaginary course through visual observation of a cathode ray beam spot on the cathode ray tube screen (as in actual train-elevation tracking radarscopes), through the manipulation of train and elevation controls such as dials or the like. The course of an imaginary target is fed into the cathode ray tube as an electrical signal, varying in accordance with a desired course pattern, to impress varying tracking signals across the twopairs of cathode ray beam dellecting plates of the cathode ray tube and to cause a vertical and/or horizontal deiiection of the cathode ray beam spot on the cathode ray tube screen, representing the resultant of the train and/or elevation components of a desired target course. Proper manipulation of the control dials bythe trainee results in a decrease in the signals thus applied across the beam deecting plates to decrease the deection of the cathode ray beam spot. 'Il-lus, the imaginary course of an imaginary .target is represented by a deflection of the cathode ray beam or target tracking spot, while the trainee attemptstotrack the imaginary target along its course by manipulation of the control dials to maintain the spot at or close to its zero deliection point.

The present instrument is also provided with a jitter generator unit, which produces relatively small varying and vibrating signals across the cathode ray beam detiecting plates, to impress a slight Wander motion on the target tracking spot and to superimpose a vibratory or jitter action upon this wander path, Ithus alfording a realistic simulation of the actual appearance of the type of radarscope screen'being imitated. In the use of an actual radarscope of the type here concerned, if the target leaves the scopes tra-cking field, or if the tracking is so inaccurate as to permit the target to pass out of the scopes field, the scope attains an ietf-target condition wherein the tracking spot immediately attains a substantially annular form which wanders into a substantially central position on the screen. The off-target condition continues until the field of the radarscope is again placed on-target, whereupon the tracking spot is again formed on the screen and the usual tracking operation may be continued. Therefore, to further simulate actual radarscope operation, the present instrument is provided with a spot returner unit operating to convert the tracking spot into a substantially annular form when the tracking spot, representing the imaginary target, passes outside an onl United States Patent ice target area defined on the cathode ray tube screen, and further operates to cause the annular form to generally Wander toward a central position on the cathode ray tube screen. A caging mechanism is also provided in the present instrument for operation in conjunction with the spot returner unit, and functions to enable a return to ontarget condition after the Off-target condition has occurred.

In order to determine the proliciency of a trainee in tracking an imaginary target, the present instrument is provided with a scoring system, which operates to define an accurate tracking area on the cathode ray tube screen. So long as the trainee is tracking the imaginary target with sutiicient accuracy to keep the tracking spot within the accurate tracking area so dened, the scoring system registers accurate tracking; while if the tracking error is so great as to cause the tracking spot to exceed the limits of said area, the scoring system stops registering. Thus, there is provided a determinati-on of the portion of the ltracking time during which accurate tracking was obtained.

It is therefore, one object of the present invention to provide an instrument for training in and demonstrating radar tracking which simulates the conditions of actual radar tracking in train and elevation and the operation of an actual train-elevation tracking radarscope.

Another object ofthe present invention is to provide an instrument for training and demonstrating radar trackingl which enables a trainee to track an imaginary target along an imaginary target course ina manner similar to actual radar tracking.

Another object of the Vpresent invention is to provide 'an instrument for training in and demonstrating radar tracking whose visual target tracking reference is caused to wander and vibrate about its position, as does the target tracking reference on an actual radarscope screen.

Another object .ofthe present invention is to provide an instrument for training in and demonstrating radar tracking Whose tracking screen has an on-target area ldefined thereon, and Whose circuit operates to change the visual target tracking reference spot into a substantially annular form upon thetarget tracking reference exceeding'the limits of the area so defined, similar to the oittarget condition lof an actual train-elevation tracking -radarscope Another object of the present invention is to provide an instrument for training in and demonstrating radar tracking which enables a return of the instrument to an on-targe condition when the above-mentioned ofttarget condition has occurred.

A still' further object of the present invention is to provide a scoring system which, when operating in conjunction with such an instrument as afore-described, functions to approximate a circular area, in the form of a substantially regular Octagon, upon the cathode ray tube screen as an accurate tracking area, to register accura-te tracking when the target tracking spot is within the area so defined.

Still another object of the present invention is to provide a differential amplifier which functions to decrease the potential in lone output circuit thereof proportionately to the increase in potential of the other output circuit thereof in response to an input signal, and which operates in the tracking circuit of the present instrument to increase the tracking signal applied to one of a pair of the cathode ray beam deecting plates and to proportionately decrease the signal .applied to the other plate of the pair.

Having thus indicated in a general Way 'the purposes, objects, functions, and operation of the present invention, a more adequate understanding thereof can be had from a consideration ofthe detailed description of one` v embodiment of the present invention made hereinbelow in conjunction with the accompanying drawings, in which like reference charac-ters ref er to like or corresponding parts and wherein:

lFig. 1 is a schematic blockdiagram of the several components of the present instrument and schematically illustrates their interrelation;

Figs. 2, 3, 4, 5, 6, 7, and 8 are detailed wiring diagrams of the director and course unit, the phase sensi- -tive detector unit, the differential amplifier, the cathode ray tube, the scoring system, the spot returner unit, and the jitter generator respectively, of the present invention as indicated on the several drawings; and

'Fig'. 9 is a detailed wiring diagram of a caging mechanism of the presen-t instrument illustrating in Ka partially schematic and partially detailed manner the interrelation of the caging mechanism with the several portions of the present instrument and of their interrelation with each other.

Tracking circuit The tracking circuit of the present instrument in general comprises a director and course unit 100, whose output is'fed into ya phase sensitive detector 200, the output of which is amplified in the amplifier 300 and then fed to the beam deflecting plates of the cath-ode lray tube 400, as illustrated in the block diagram Fig. l.v This circuit is made up of two substantially identical systems, one for tracking in ltrain and the other for tracking in elevation, the resultant output of each being applied to a different pair of cathode ray tube beam deflecting plates. The director and course unit 100 comprises two pairs of synchronously connected `generators connected to form ltwo control transformer systems, one pair including the train director 110 and the train control transformer 120, while the other pair inclu-des the eleva-tion director 130 and the elevation control transformer 1'40., Train course cam 151 and elevation course 1cam 151a :and ltheir operating motor 150 are included in the director 4and course unit. These cams are mechanically connected to the rotors of the train and elevation control transformers 120 and 140 respectively, and operate lto establish an imaginary target course for the trainee -to track. As these cams are -driven by the motor, desired rotational patterns of the control transformer rotors yare obtained in accordance with the contours of the cams, and yas the rotors are moved out of synchronous relationship with the `positions of the rotors in their respective director uni-ts 110 and `130, separate 'train and elevation signals are generated in accordance wit-h the nonsynchronous ydisplacement of each of the control transformer rotors with respect to its corresponding -director rotor. The sign-als thus generated are fed into the phase sensitive detector 200, the train signal being fed into the train portion 291 of the detector and the elevation signal into the elevation portion 251, where the phase of the signals generated by the director `and course unit are determined to establish the direction of nonsynchronous displacement between the corresponding directors land control transformers. The train output of the phase sensitive detector is then amplied in the train portion 301 of amplier 300, and the elevation output is amplified in the elevat-ion portion 351 thereof before being applied to their respective pairs o'f cathode ray tube beam deecting plates. A cathode ray lbeam spot or visual 4trackingreference on the cathode ray tube screen is thus deflected from an established central position or null point in accordance 'with the nonsynchronous displacement of the train and elevation control transformer rotors with respect to their corresponding director rotors and the-.signals resulting therefrom. The trainee observes the deflection of the spot on the cathode ray -tube screen, representing a target course, and attempts to follow this course by keeping the spot in the central portion of a reticle or `area defined on the cathode ray tube screen. This tracking is accomplished 'by the trainee manipulating train and elevation control dia-ls 1-10a and 130a or other control means to rotate the train and elevation director rotors, respectively. Proper manipulation of these dials operates to rotate the director rotors into synchronous position with the displaced control transformer rotors, ythereby reducing the director course unit output signal, and hence reducing the deflection of the spot or reference on the cathode yray tubescreen. Thus, as an imaginary target course is described by the-action of the course cams and their motor on the control transformer rotors and is observed by the position of the spot on the cathode ray tube screen, the trainee attempts to maintain an on-target positioned by manipulation of the train and elevation control dials to cause -t'he train and elevation director rotors to follow this course.

lConsidering the tracking circuit in detail, and for this purpose referring first to the detailed wiring diagram of the director and course unit shown in Fig. 2, the stator 11 of the train director 110 is synchronously connected through the reversing switch 115 to the stator 121 of the train control transformer 120, and an A. C. voltage is impressed across the rotor 112 of the train director to form a conventional control transformer system. When the position of rotor 122 is synchronised with that'of rotor 112, no voltage is impressed across the former. Energzation of the course cam motor 150 causes a rotation of the rotor 122 of the train control transformer 126, as determined by the train course cam 151, to a nonsynchronous position with respect to the director rotor 112, `resulting in an A. C. voltage being impressed across the rotor 122 in accordance with the nonsynchronous displacement, the phase of said voltage being determined by the direction of nonsynchronous displacement. The

' voltage thus produced is impressed across the potentiometer 160, and a portion is tapped therefrom and applied across the seriesof resistors 162, 163, 164, and 1165. The purpose of the reversing switch 115 is to enable thc cam 151 to present two target' courses in train, either from left to right or right to left, 'for a single cam contour. The purpose of the potentiometer 160 is to divide the train control transformer output to provide a conversion from train to traverse as is necessary for diiferent target elevations. The potentiometer tap- 161 is therefore mechanically linked to the elevation course cam 15161 to continuously accomplish this conversion as the elevation of the imaginary target course is varied. The elevation portion of the director and course unit is substantially identical to the train portion, comprising the elevation director 136i, whose stator 131 is synchronously connected course systems is the absence of a reversing switch between the elevation director and the elevation control transformer (which may be supplied if desired) and of a potentiometer in the elevation control transformer output circuit. Thus, upon theenergization of the course cam motor 150, an imaginary target course is dened by rotation of the train and elevation control transformer rotors 12.2 and1d2, as controlled by the contours of the course cams 151 and 15in. As the trainee attempts to track the course so. described by manipulating the control dials 11911 and e to rotate the director rotors 112 and 132 in synchronism with the control transformer rotors 122 and 142, an output is'obtained from the train and elevation control transformer rotors in accordance with the train and elevation tracking errors, or in accordance with the nonsynchronous displacements between the director rotors and their corresponding control transformer rotors, Error signal voltages are thus produced and impressed acrossthe above-mentioneditwo series of resistors for the corresponding-portions of the `director and course unit. If desired, a greater correction of tracking error per unit turn ofthe elevation control dial than of the train control dial may be had, or vice versawhen it is considered advantageous, by appropriately gearing the dials to their respective director rotors.

'Ihe error signals of the director and course unit, as tapped oli at points A, B, and C fortrain and points D, E, and F for-elevation, are applied to the phase sensitive detector unit as indicated in the detailed wiring diagram thereof in Fig. 3. Considering the train portion of the detector, it includes the two vacuum tubes 220 and 230: tube 220 being a twin diode having the cathodes 221 and 221e and the plates 222 and 223, functioning as a voltage limiter for the train portion of the detector circuit; tube 230 being a twin triode having the cathodes 231 and 231er, the grids 232 and 234, and the plates 233 and 235, functioning as a phase detector for the train portion of the phase sensitive detector unit. The limiter tube 220 is biased by means of theB-(l) supply to make the plates 222 and 223 thereof more negative than the cathodes 221 and 221a, as determined by the ratio of the resistors 224 and 225, leaving the tube 220 nonconductive when no trackingerror voltage is applied to the points A, B, and C. When an A. C. voltage signal is generated across the train control transformer rotor 122, an A. C. voltage is impressed thereby across the series of resistors 162, 163, 164, and 165, and during one half of such an alternating voltage cycle the point A attains a more positive and the point C a more negative potential than point B, while during the other half of the cycle point C attains a more positive and point A a more negative potential than point B. So long as the potential difference between points C and B and between points A and B is small, or so long as the voltage generated across the train control transformer `rotor 122 is small, the above-mentioned B- bias on the tube 220 is not overcome and the tube remains nonconductive, permitting the potentials of the plates 222 and 223 to fluctuate with respect to point B -in direct correspondence with the tracking error signal. Howevenwhen the potential at point A or C exceeds a determined positive value with respect to that at point B, as may be caused by a large train tracking error, the B- bias is overcome on that half ofthe limiter tube 220, and this tube then becomes conductive v limit value, the tube 220 becomes conductive to both` plates alternately in correspondence with the voltage cycle alterations. Thus, the limiter tube 220 functions to limit the potential differences between plate222 and' point B and between plate 223 and point B to a peak beyond which they cannot increase substantially despite an increase in tracking error. This limiting `potential difference is determined by the initial bias or potential diterence impressed upon the plates and cathodes of limiter tube 220.

Referring to detector tube 230, the B-(1) supply eslishes the plates 233 and 235 at approximately ground potential, the grids 231 and 234 at approximately B*(l) potential, and the cathodes 231 and 231e at 'a value intermediate that of the grids and plates as determined by resistors 226 and 227. A stepdown transformer 240 is connected at points G and H to the A. C. voltage supply fed to the director and course unit, and the voltage from the secondary thereof is superimposed upon the B- potential fed to the cathodes of tube 230 to `shift their potential with respect to their grids and plates in accordance withthis superimposed voltage fluctuation. As'surning for the moment zero signal voltage from the control transformer 120, the alternating voltage impressed upon the secondary of the transformer 240 operates on one half of the voltage cycle to shift the cathodes 231 and 231e of the tube 230 more negative, the magnitude of negative lshift of the cathodes being determined by that of the secondary voltage and the ratio of the resistor 226 to the resistor 227, and on the other half of the voltage cycle to shift said cathodes more positive by a like amount, although the grids at all times remain negative with respect to the cathodes. The Values of this circuit are so chosen as to cause a small ilow of current through tube 230 to both plates equally during the portion of the superimposed A. C. cycle which shifts the cathode potential more negative than its D. C. level.

Upon the occurrence of a train tracking error signal, during one half of the error signal voltage cycle point A is negative with respect to point B, and point C is positive with respect thereto, thus shifting the grid 232 more negative and the grid 234 more positive than their D. C. bias, and if during that half of this signal voltage cycle the voltage impressed upon the secondary of the transformer 240, which is in time phase with the control transformer produced signal, is such as to shift the cathodes 231 and 231a more negative than its D. C. level, an increased electron current ow occurs from the cathode 23111 to the plate 235 while the current flow from cathode 231 .to plate 233 is decreased or completely extinguished. During the next half of the signal and transformer voltage cycle, point C becomes negative with respect to point B Kand point A becomes positive with respect thereto, causing the grid 232 to shift more positive and the grid 234 more negative than their D. C. bias; but because of the time phase relationship between the transformer voltage and the signal voltage, the transformer produced voltage is operating during this half of the cycle to shift the cathodes more positive than their D. C. level, hence counterbalancing the eiect of the signal voltage and preventing the ow of any electron current from the cathodes to the plates. The tube 230 therefore becomes nonconductive during this half of the Voltage cycle. If the train tracking error is in the reverse direction, the phase of the control `transformer signal voltage is inverted, and as is apparent from the foregoing description of the present circuit, the phase detector tube 230 becomes increasingly conductive during one half of each A. C. voltage cycle from its cathode 231 to its plate 233, rather than from cathode 231a to theV plate 235 as in the above description. Thus, the tube 230 operates to detect the train tracking error signal and to indicate the direction of tracking error. Due to the above-described action of the limiter tube 220, a limit is established on the extent to which the grids 232 and 234 may shift in a positive direction from their D. C. bias as a result of tracking error signal, hence the current llow from the cathodes to the plates of tube 230 is accordingly limited, limiting the maximum error signal passed by the phase sensitive detector unit 200.

Thus, when the error signal generated by the train control transformer is in such -a direction as to cause increased D. C. current to flow intermittently from the cathode 23111 to the plate 235 of the detector tube 23), the increased current ow through the resistor 238, potentiometer 237, and the tap 239 to ground causes point J to become more negative than point l. When the train tracking error is inthe opposite direction, the resultant error voltage phase version causes increased intermittent v D; C. current to flow from the cathode 231 to the plate 233, and hence the increased current ow through the resistor 236, `potentiometer 237, and the tap 239 to ground causes point I to become more negative than point J. Therefore, upon the occurrence of a train tracking error, avpul-sating intermittent D.r C. potential ditference'is created between points I and J, whose magnitude is dependent upon the magnitude of train tracking error up to a maximum limit established by the characteristics of the limiter tube 220 and its circuit, in a direction determined by the direction of the train trackng'error and established by the operation of the phase'detector tube 236 and its circuit. The potentiometer 237 and its variable tap 239 are provided to establish an exact bal-ance in the resistance bridge across the plates 233 and 235 of tube 238 and to compensate for any unequal output of the two halves of tube 238 when no train tracking error signal voltage is impressed lat points A, B, and C.

The elevation portion of the phase sensitive detector circuit is identical to the train portion described above, comprising the limiter tube 250 and the phase detector tube 260, functioning upon the application of an elevation tracking error signal to the points D, E, and F in the `same manner as the corresponding tubes 220 and 238 in the train portion of the circuitto create a potential difference between the points K and L.

The intermittent pulsating voltage outputs of the phase sensitive detector unit at points I, I, K, and L are applied to the amplifier 308 through its input bridges 240 and 241, shown in the detailed wiring diagram Fig. k4. Considering in detail the -train portion of the amplifier, it comprises the twin triode amplifier tube 310, having the cathodes 311 and 311a, the grids 312 and 313, theplates 314 and 315, and the cathode load resistor 316. The B-(l) supply is connected to the eathodes 311 and 311:1 through the cathode load resistor 316, to the grids 312 and 313 through the resistors 290 and 291, and to points I and J and the plates 233 and 235 of detector tube 230 (see Fig. 3) through the amplifier input bridge 240, although having a negligible effect on the latter because of the large impedance of the bridge 240, while the B+(1) supply is connected to the plates 314 and 315 through the plate load resistors 317, 318, and 3.19. The values of the B supplies and of the elements of this circuit are so chosen as to establish the cathodes 311 and 311:1 at approximately ground potential and at a positive potential with respect to the grids 312 and 313, and to estab. lish the tube 316 with a desired flow of electrons from its cathodes 311 and 311e to its plates 314 and 31S respectively. Upon the occurrence of a train tracking error, the potential difference resulting between points I and J from the operation of the phase detector tube 230 is ap plied across amplifier tube grids 312 and 313, after being smoothed into a substantially steady D. C. potential by means of the filters comprising resistor 280 and condenser 284 connected to ground and resistor 282 and condenser 285 connected to ground. Upon the occurrence of a' negative potential shift at point I and a positive shift at point I as a result of a train tracking error, the potential on grid 312 of the tube 310 is correspondingly shifted in negative direction to decrease the electron ow from cathode 311 to plate 314 while grid 313 is'correspondingly shifted in a positive direction but by a less amount than thc shift of grid 312 (because the potential shifts at points l and l are not of equal magnitude) to increase current llow from cathode 311a to plate 315. The amplifier tube 310 being connected to function as a cathode'follower, the potential on the connected cathodes 311 and 311a is accordingly shifted in a negative direction resulting in a greater ow of electrons from the cathode 31111 to the plate 31S of tube 310 than would result solely from the positive potential shift of grid`313. The potential on plate 315 and at point N therefore shifts in a negative direction while that on plate 314 and at point M correspondingly shifts in more positive direction. VIf the train tracking error is in such direction as to result in negative increase of potential at point J and a positive increase at point I, it is therefore apparent from the foregoing analysis that the potential on plate 314 and at point M shiftsin a negative direction and, that on plate 31S and at point N correspondingly shifts in a positive direc-y tion.v This amplifier, therefore functions substantially as a true dierential arnplier when the impedance for each half of its output bridge comprising resistors 318 and 319 are equaLcauSing substantially equal but inverse variations in its two plate potentials for a signal applied to one of its control grids. The condensers 292 and 293 connected across' the resistors 290 and 291, respectively, function to further steady the linearity of the voltages applied to the cathodes and grids of tube 310.

lf desired, either of the condensers 286 or 287 of different capacitance values may be connected across the amplifier tube feed-in bridge 240 through the resistor 288 and the selector switch 289, cooperating with resistors 281 or 283 to damp partially variations in the potential difference between points I and J or to damp partially the eiect of variations in train tracking error. When the values for condensers 286 and 287 and resistors 288 and 281 or 283 are properly chosen, a desired fraction of potential dilerence change between points I and I is damped, thereby resulting in the simulation of automatic lead of the target as is frequently employed ingun director systems. As the trainee adjusts the train director to compensate for movement of the target and eliminate a tracking error signal, the initial potential difference change between points I and I are damped and no noticeable etect is had on the cathode ray tube screen, corresponding to the lag of the gun director With respect to the-gun to provide the lead angle. Variations in rate of manipulations of the train director 110 are correspondingly affected to simulate the effect of automatic lead angle.

The elevation portion of the amplilier circuit is identical to the above-described train portion, comprising the twin triode amplier tube 330, an input bridge 241 therefor, and an output bridge therefor. The elevation portion of this circuit thus lfunctions in a manner identical to the train portion, so that the application of a negative potential at point K with respect to point L resulting from elevation tracking error and the operation of the phase detector tube 260 causes the potential at point P to shift in a negative direction and that at point O to shift in a positive direction, while the application of negative potential at point L with respect to point K causes the potential at point O to shift'in a negative direction and that at point P to shift in a positive direction. Ampliertube 330, therefore, also functions as a dilerential amplifier in the same manner as tube 310. Thus, upon the occurrence of a tracking error either in train or elevation, the direction of the error-is established by the phase sensitive detector circuit, and the error signal issuing from the detector is then amplified in the amplifier circuit to establish a potential difference between points M and N for train tracking error and points O and P for elevation tracking error, the direction of the potential difference in each case depending upon the direction of tracking error of the respective tracking phase.

`The cathode ray tube unit 406, shown in detail in Fig. 5, like theabove-described units of the tracking circuit, is divided into two identical parts: the train error signal portion, including the horizontal beam deflecting plates 411 and 411a of the cathode ray tube 410, and the elevation error signal portion, including the vertical beam de ecting plates 412 and 412a of the cathode ray tube. Considering the cathode ray tube train input bridge 430 in detail, it comprises the resistor 431 connected to point M, resistors 432, 433, 434, and 435, and the resistor 435 connected to point N. The points M and N are established at a desired potential level'as determined by the zero train tracking error output of the amplier tube 310, thus establishing the horizontal beam deecting plates 411 and 411:1 at substantially equal and determined potential levels. However, if due to a slight unbalance in Y the input bridge 430 the potential thus established on the horizontal beam deecting plates 411 and 411a are not equal, this inequality may be overcome by the application of the B+(l) potential to the subsidiary bridge comprising the resistors 437, 433, and 434 through the variable tap 438 on resistor 437, to establish the cathode ray beam spot at the horizontal center of the tracking reticle on the cathode ray tube screen, which operation will be described subsequently. Upon the occurrence of` a potential diierence between points M and N, as would result from an error in train tracking, the error is indicatedon the cathode ray tube screen by a corresponding horizontal deection of the cathode ray beam or target tracking spot from its horizontal null point, resulting from the unequal potentials impressed upon the horizontal beam defiecting plates. Thus, any error in train tracking is represented by a horizontal deflection of the cathode ray beam spot on the cathode ray tube screen, with the direction of error'as established by the phase sensitive detector unit determining the direction of the deection. The elevation cathode ray tube input bridge 450v and its subsidiary zeroing bridge are identical to the train input and subsidiary bridges, and operate in a correspondingmanner upon the vertical beam deecting plates 412 and `412a of the cathode ray tube, to indicate the elevation ltracking error by a vertical deection of the cathode ray beam spot in a direction corresponding to the tracking error direction established by the elevation tracking error signal impressed upon the elevation input bridge 450 at points O and P. The operating potentials on the anode 413, the cathode 416, and the focus and intensity grids 414 and 415 respectively, of the cathode ray tube are established by the B-(l) and B+(l) potential sources app'lied across the resistors 417 and 418.

In order to effect a proper zeroing of the cathode ray beam spot in the tracking reticle on the cathode ray tube screen, the resistors 290 and 291 and plates 314 and 315 of tube 310 in the train portion ofthe tracking circuit and the corrseponding elements in the elevation portion are shunted by closure of tied switches 294 and 295 and tied switches 320 and 321. Closure of the lirst mentioned pair of switches results in substantially equal potentials being applied to the grids of the two amplifier tubes, and closure of the second mentioned pair of switches insures substantially equal potentials at points M and N and at point O and P, despite any unbalance in operation of the amplier tubes or inequality intheir output bridges. This being done, the outputs of the subsidiary bridges in the cathode ray tube input circuits may be adjusted by their variable taps to position the cathode ray beam spot centrally, both vertically and horizontally, in the reticle on the cathode ray tube screen, placing the cathode ray tube circuit in readiness for operation in the tracking circuit.

Scoring .system ln order to determine how effectively the trainee is tracking the imaginary target along its imaginary course, the present device is providedwith a scoring system generally indicated by the numeral 700. As previously mentioned, the object in operating the present tracking circuit is to follow the imaginary course of a target as established by the course cam 151 and its motor 150 and is indicated by the cathode ray beam spot on the screen of the cathode tube 410, the tracking errors being indicated by appropriate deections of this target tracking spot from its zero or central position within the reticle on the cathode ray tube screen. To determine the accuracy of the trainees tracking over a period `of time, the present scoring system energizes a scoring clock so long as the error signal delivered by the amplilier to the cathode ray tube deecting'plates is not great enough to cause a beam deection beyond desired established limits within the reticle. To this end, the output voltages of the amplifier at points M and N for train and O and P for elevation errors respectively, are applied to the scoring system circuit illustrated in detail in Fig. 6.

The voltages impressed at points Mand N are applied to the cathodes 711 and 712 respectively of the twin diode 710, while-the voltages `impressed at points and P are 16 applied to the cathodes 731 and 732 respectively of the twin diode 730. The plate voltages of the tubes 710 and 730 are combined and operate to control the beam power ampliiier tube 750 comprising the plate 753, cathode 752,

control grid 751 and screen grid 751a, which in turn operates the solenoid 77 0 through the one-way control tube 760. So long as the combined train and elevation tracking error signals are small, the relay 770 is energized to close the switch 771 operating the scoring clock 780, but when the combined tracking error signals exceed a predetermined amount, as indicated hereinabove, the solenoid 770 is deenergized to open the switch 771 stopping the scoring clock 780, thus permitting a determination of the accuracy of the trainees tracking over a period of time.

Considering the scoring system in detail, a B-(Z) and the B+(1) potentials are applied across the voltage dividing network comprising the resistors 720, 721, 722, and 723, from which a desired potential is tapped and applied to the plates 713, 714, 733, and 734 of the tubes 710 Vand 730 more positive than that impressed upon thefcathodes 711, 712, '731, and 732 thereof from the points M, N, O, and P. A desired bias is placed on the grid 751 of the beam power amplifier 750, as determined by the position of the tap 724 on the resistor 721, to make the grid 751 negative with respect to the grounded cathode 752 and to cause a desired current to flow from the cathode 752 to the anode 753 thereof connected to the B+(2) potential source through resistor 754. The resultant plate current through the plate load resistor 754 establishes the cathodes 761 of the duo-diode control tube 760 at 'a more negative potential than the plates 762 thereof, connected through the solenoid coil 770 to a B+(3) plate supply, thus energizing the relay 770 to close the switch 771 and hence operate the scoring clock 780.

Considering in detail the operation of the tube 710 and its eiect upon the voltage network operating to control the bias on the grid 751, the plates 713 and 714 thereof are tied together and hence must always be at the same potential. .Prior to any train tracking error signal at points M and N, the cathodes 711 and 712 are established at the same potential, negative with respect to that impressed upon the plates 713 and 714, causing a current flow in the plate circuit. Since the plate load resistor 716 is very large as compared with the internal resistance of the tube 710, the plates 713 and 714 are caused to tide at a potential just slightly more positive than that impressed upon the cathodes of the tube and the potential at point 715 is equal thereto. Upon the occurrence of a train tracking error signal, the potential on one of the cathodes shifts in a negative direction while the other shifts in a positive direction, and the more negative cathode controls the plate potential to make it shift in the negative direction in accordance therewith, hence causingthe potential at point 715 to shift correspondingly in a negative direction and cutting olf the flow of electrons from the more positive cathode to its plate. This negative potential shift is combined with the B-(Z) and B+(l) potentials in the abovementioned voltage divider network to correspondingly shift the potential on the control grid 751 of the amplier tube 750, and as the train tracking error increases the grid 751 is caused to shift correspondingly more negative. As grid 75l rides more negative, the flow of elec- -trons from the cathode 752 to the plate 753 is accordingly decreased, causing the potential on plate 753 to shift in a positive direction. Since the cathodes 761 of the control tube 760 are tied to the plate 753 of tube 750, the potential thereon correspondingly shifts in a positive direction. As the train tracking error continues to increase, the potential difference between the cathodes 761 and plates 762 diminishes to the cut off value of the tube 760, thereby deenergizing the relay 770 to stop the scoring clock 780. Thus, when the train track# ing error signalv exceeds a. predetermined amount as established by the interrelation of the operating voltage supplies and values of the elements in the present scoring system, the scoring clock is stopped to indicate that the trainee is not tracking the imaginary target accurately. The action of the tube 730 upon this circuit is identical to that of the tube 710, but operates in response to the elevation amplifier tube 33t)y to establish an accurate elevation tracking error limit in response to the potential difference existing between the points O and P.

When both train and elevation tracking errors are present, the two tubes 710 and 736 continue to operate in the same manner as described above, but the potentials at point 715, representing train tracking error, and at point 735, representing elevation tracking error, are combined in the voltage divider network 725, and it is the combined potential which acts upon the remainder of the scoring system circuit inthe same manner as for the individual tube action. The ideal situation for scoring accurate tracking would be to define the accurate tracking area as a circular area described on the cathode ray tube screen within and concentric with the tracking reticle. The means here employed for combining the train and elevation tracking error signals is such as to approximate this ideal condition by defining the accurate tracking area in substantially the shape of a regular octagon with the zero tracking error position of the tracking spot located equidistant from its apexes, This is accomplished by making the three plate load resistors 716, 723, and 736 of equal value and each being greatly in excess of the internal resistance of the tubes 710 and 730. If resistors 716 and 736 were made very small with respect to the resistor 723, the larger of the two potentials carried at points 715 and 735 would completely control variations in the bias of the control grid 751, and would therefore result in an accurate tracking area on the cathode ray tube screen being defined substantially in the form of a square, registering inaccurate tracking only when either the train or elevation tracking error became so great as to exceed the established limit, although smaller tracking errors in train and elevation when combined would indicate inaccurate tracking on the cathode ray tube screen if the accurate tracking area is there defined as a circle. On the other hand, if resistors 716 and 736 are made very large with respect to resistor 723, the combined train and elevation tracking error signals would be completely additive f to register faulty tracking onthe scoring clock while the spot on the cathode ray tube screen would still be within a circular accurate tracking area. The area defined by such an additive system would be substantially in the form of a diamond with its apexes located midway between the apexes of the above-mentioned square area. However, if resistors 716, 736, and 723 are all made equal, a compromise is obtained between these areas. Such is the situation in the present scoring system, and the potentials obtained at points '715 and 735 as a result of train and elevation tracking errors are combined in such a manner as to control the scoring system to indicate accurate tracking so long as the cathode ray beam spot on the cathode ray tube screen remains within an area defined substantially in the form of a regular octagon. By adjustment of tap 724 on the resistor 721, various octagonal areas may be defined to describe the limits of accurate tracking so far as the operation of the scoring clock is concerned. When the combined potentials carried by the plates of tubes 710 and 736 exceed a predetermined value, as determined by the position of this tap, such'that the combined train and elevation tracking error is sufficient to deliect the cathode ray beam spot outside the accurate tracking limit defined by the scoring system, the control grid 751 of the amplifier 750 is' impressed with a sufficiently negative potential to cut oft conduction through the control tube 760, and hence the relay 774)v is deenergized to stop the operation of the scoring clock 780. Thus, there is presented a scoring system which determines an accurate tracking area on the cathode ray tube screen substantially in the form of a regular Octagon, approximating the ideal condition of a circular area, and which operates to control a scoring clock to indicate the portion of a period of time that the trainee has obtained accurate tracking of the imaginary target course, or the portion of a period of time that the trainee has followed the imaginary target course with suiiicient accuracy to keep the cathode ray beam spot within the accurate tracking area defined. by the scoring system.

Considering the control tube 760 and its operation in detail, a B+ potential from the B+(3) supply is im pressed upon its plates 762 through a plate load resistor comprising the coil of the relay '770, while its cathodes '761 are impressed with the potential carried by the plate 753 of the amplifier tube 750. The purpose of this control tube is two-fold: first, since the relay 770 can operate when current flows through its coil in either direction, tube 760 operates as a one-way valve or rectifier to permit energization of this coil only when the plate 753 of tube 750 is a determined amount more negative than the B+ potential on plates 762 and to prevent energization of the coil when the plate 753 becomes more positive than that B+ potential, as is obviously necessitated by the operation of the present scoring system; second, this control tube further functions to limit the effective activity of the amplifier tube 750 to the linear portion of its plate current-voltage rcharacteristic curve, and this is accomplished through a proper selection of values for the B+(3) and the B+(2) supplies, for by establishing the proper voltage differential between B+(l) and B+(2) the conduction potential range for the cathodes 761 of tube 760 are established to lie on the linear portion of the plate current-voltage characteristic curve for the amplifier tube 750. The condenser 763 is connected across the solenoid 770 to filter the current flowing in the plate circuit of tube 760.

Jtter generator As indicated earlier in the specification in the general discussion of the present instrument, a'jitter generator is provided for the purpose of impressing an irregular relatively small wander motion to the cathode ray beam spot on the cathode ray tube screen and for superimposing upon this wander motion a vibratory or jitter action, thereby simulating the actual conditions generally existing on the screen of a train-elevation radarscope. This jitter generator, generally denoted by the numeral 500, is illustrated in detail in Fig. 8 and generally comprises a plurality of gaseous discharge tubes, as for example neon discharge tubes, each shunted by ya condenser across its discharge plates and having resistors cooperating therewith to provide a plurality of relaxation oscillators. These oscillators are grouped into pairs with each pair operating to vary the potentials of the control grids of `a twin triode amplifier to control the plate potentials thereof. The two plate potentials of each amplifier tube are combined and impressed upon one beam deflecting plate of the/cathode ray tube.y By employing condensers of different capacitances and rcsistors of different ohmages in conjunction with the several discharge tubes, different yand irregularly varying potentials are impressed upon the control grids of the several amplifier tubes, and correspondingly varying and irregular combined plate potentials are produced by each amplifier tube and upon the cathode ray beam deflecting plate. By providing four of such oscillatorand amplifier tube circuits, each acting upon a cathode ray beam deflecting plate, a relatively vsmall and irregular wander -er tube 530.

, different time cycles. v

, 13 motion is impressed on the cathode ray beam'Y spot on the cathode ray tube screen `and avibratory or jitter motin is Vsuperimposed thereon. v

Considering the jitter generator in detail,` it comprises t four oscillatorv and amplifier tube circuits indicated by the numerals 501, 502, 503, and G14, leach impressing a voltage resulting from the combination of the amplifier tube plate` voltages upon a cathode` ra'y beam deecting plate, by connection thereto through the points A', B', C', and D. Referring particularly to the circuit generally denoted by the numeral 5131, it comprises the two gaseous discharge tubes 510 and 526i and the twin triode ampli- A vpositive potential from the B+(3) supply is impressed'upon the plate`513 of the discharge tube 510 through the -`resistor Sill, while the opposing plate 514 thereof is connected `to ground. These two plates are shunted by the condenser 512; therefore, when the 4B+(3) potential is lapplied to the plate 513 the condenser 512 commences to charge until a sutcient potential difference across lthe plates 513 and S14 is reached to ioniz'e the tube 510 and hence discharge the condenser 5.12 until the tube is deionized. This process is con; tinuall'yl repeated, causing an intermittent discharging of the tube 510 which resultsvin analternate charging and discharging of the condenser 512, the time interval between discharges of the tube 510 being dependent upon the value of the' ltt'a)` source, the value ofrlesistor 511, the characteristics of the discharge tube 10, 'and the capacitance of the condenser 512. ljischarge tube 520 is apart of a similar relaxation oscillator circuit, having resistor 5251 interposed between its plate 523 and the l3+(3) supply and a condenser 522 shunted across itsplates 523 and 524, plate 526i being connected to ground. The plate-s S31 and 532 of the twin triode amplifier tube 530 are established at a positive potential through the circuit comprising theBtG) supply, resistor 54), potentiometers 541, and '542, and 'the blocking condenser 543, its cathode 535 is ixed at ground potential, and its control Vgrids 533 and 534 fluctuate in potential in accordance with the charge carried by the blocking condensers 515 and 525 interposed between `these grids and the plates 513 and S23 of tubeslt) and 520. Thus, as a'positive potential is applied to the plate-5l3 of discharge tube 510, the condensersl "and 515 increase in charge over a period of time causing'the grid 533 to becomeV more negative in accordance withthe increasing charges on the condensers as applied thereto through resistor 536 connected to ground; and upon discharge'of the tbe 510, the condensers S12 and 515 rapidly discharge therewith causing the grid 533 to rapidly Vundergo afdecrease in negative potential. Simultaneously with this operation ofthe discharge tube Sie, the relaxation oscillator comprising tube 52tl`operates in a similar manner-upon grid 534 of tube 5393, the potential carried-by blocking condenser 525 being applied Vto the grid. 5.3?, through resistor 537 connected to.v ground. Sincekthe several'c'ondensers and resistors included in the two halvesof the circuit 50i are chosen `of different values, the potentials of the grids 533 and 534i which vary independently of each other do so on The plate potentials foreach half ofthe amplilier tube 53thv vary in direct time relationship but in inverse voltage relationshipwith the fluctuations of the potentials 'carried by their respective control grids, and about avpoten` tial level asl determined bythe BH3)l supply and the plate load resistance comprising resistor Sdi), potentiometer 541, and resistor 538 for one plate and resistor 539 forthe other plate. The variations in the two plate potentials are then' combined through the resistors S50, 551, and 552, and the combined potential tluctuations are damped or filtered to a desired degree by means ofthe condensers 553 and 554. Also,` a blocking condenser 555 is interposed between resistor 552 and point D to block the operating D. C. current of the amplifier tube` 53d. The `irregularly fluctuating potential thus lapplied at point p D is superimposed uponV the potentiel carried by the beam devecting plate 412er from other sources described above.

The other circuits of the jitter generator indicated by the numerals 502, 503, and 504 are substantially identical to the above-described circuit 501, and the operation of each of these circuits will be apparent to one skilled in the art from a consideration of the above-description. However, the values of the condensers and resistors associated with each ofthese circuits are preferably chosen of dilerent values from any other corresponding circuit in order that the potentials carried at points A', B', C', and B may each uctuate to a different extent and in a different time cycle than the potential at any of the other points. Thus, the irregularly and independently fluctuating potentials impressed upon points A', B', C', and D are superimposed upon the potentials carried by the beam deecting plates Mia, dll, 412 and 412a respectively, causing the cathode ray beam spot on the cathode ray tube screen to Wander about its position as a function of charging of the condenser of the relaxation oscillators and to vibrate or jitter along its wander path as a function of discharging of the condensers of the oscillators.

Spot returner unit As indicated in preceding portions of the present specitication, the trainees proiciency in tracking the imaginary target is registered by the scoring system 700, op erating to indicate the portion of a period of time in which the trainee followed the imaginary target within a given field of accuracy. However, when tracking errors exceed the limits so delined, no effect is had upon the tracking circuit, only the scoring clock being deenergized. In order to further simulate an actual train-elevation tracking radarscope, the present device is provided with a` spot returner unit, lgenerally indicated by the numeral litt) and illustrated in detail in Fig. 7, which denes an on target area with relation to the cathode ray tube screen beyond the limits established by the scoring system. This unit operates in such a manner that when the combined train and elevation tracking errors cause the cathode ray beam spot on the cathode ray tube screen to be deflected beyond the limits deiined by it, as corresponds to a tracking error which would put a radar-scope ott target, the spot on the cathode ray tube screen is caused to change into an annular form and to slowly Wander generally in the direction of the center or null point of the tracking reticle. 4

To these ends, the present spot returner circuit 60) is provided with a pair of twin triode'tracking error signal detector tubes 610 and 620 for train and elevation tracking error signals respectively, whose combined output controls the amplifier tube 640 to regulate the twin triode cathode follower control tubes 650 and 670 Also, a resistance-capacitance phase splitting bridge 65th operates through theV twin triode amplifier 690 to impress two V60 cycle voltages, displaced from each other by 90 electrical degrees, upon the grids of the control tubes 656 and 67! for producing the annular trace on the cathode ray tube screen when the trackingerror exceeds the abovementioned predetermined on target limits,

Considering the spot returner circuit in detail, the voltages carried by the tracking circuit amplifier input bridges at points R and S for train and points T and U for elevation are impressed .upon the grids 611 and` 612 for the train tracking error signal detector tube 610 and grids 621 and 622 for the elevation tracking error signal detector tube 620. The cathodes 613, 61311, 623 and 623m of these tubes are established at a negative potential level as determined by the current tiow from the B(2) source through resistors 624 and 624:1 to ground, While the plates 614 and 615 of tube 610 and the plates 625 and 626 of tube 620, all tied together, are established at a positive potential level Vby the cooperation of the B+(2) and B-(l) supplies through the resistors 616, 617, and 618. The potentials so impressed upon the cathodes and plates of these two detector tubes are so chosen as to place the tube below its cutoff point when zero tracking error signal occurs, or when the points R and S, and T and U, and consequently the grids of these two tubes, are at their no tracking error potentials. Upon the occurrence of 'a train tracking error in such a direction, for example, as to make point R more positive than its zero tracking error potential, tube 610 becomes conductive from its cathode 613 to its plate 614, Since all the plates 614, 615, 625, and 626 of tubes 610 and 620 are tied together, the potential of all these plates shifts in a negative direction. Upon the occurrence of an elevation tracking error, tube 620 responds in a similar manner causing said plates to similarly shift in a negative direction. Upon the occurrence of both train and elevation tracking errors, the larger error primarily controls the negative potential shift of the plates.

Since the plates of tubes 610 and 620 are connected to the grid 641 of the amplifier tube 640, its potential varies in response to potential variations of said plates. The cathode 642 of this tube is connected to ground, while the plate 643 thereof is connected to the B+(l) supply through the plate load resistor 644. Under zero tracking error conditions, the values for the B+(l) source and the potential of grid 641 of tube 640 are so chosen as to make the tube conductive. Upon the occurrence of a tracking error signal Iin the tracking circuit, the potential shift of the plates of the tubes 610 and 620 in a negative direction correspondingly shifts the potential of the grid 641, resulting in an increase in the positive potential of the plate 643 of tube 640; hence, increases in tracking error result in corresponding increases in the positive potential of the plate 643, while decreasesl in tracking error result in corresponding decreases in Vthe positive potential of plate 643.

The plate 643 is connected to the grids 651 and 652 of control tube 650 and to the grids 671 and 672 of control tube 670, causing the potentials of-these grids to shift in accordance with the potential of the plate 643. Each of the plates 653 and 654 of tube 650, and 673 and 674 of tube 670 are connected directly to a B+(4) supply, while the cathodes 655 and 656 of tube 650, and 676 and 675 of tube 670 are connected to the cathode ray beam deecting plates through their input bridges at points V, W, X, and Y. The potential of plate 643 for zero tracking error and the B+(4) potential source for the plates of tubes 650 and 670 are so chosen as to place both of these latter tubes below their cut oft point. However, upon the occurrence of a tracking error signal, plate 643 becomes more positive than under the condition of zero tracking error signal, causing the grids 651, 652, 671 and 672 to shift in potential therewith, and when either the train or elevation tracking error signal exceeds a predetermined amount as established by the interrelation of the various elements and voltage sources of the present spot returner unit, both tubes- 650 and 670 become conductive from each of their cathodes to the respective plates.

Before analyzing the effect of tubes 650 and 670 upon the tracking circuit, attention is directed to the phase' splitting circuit comprising the phase splitting bridge 680 and the amplifier tube 690. The bridge 680 is a conventional condenser-resistor 90 degree phase splitting bridge operating to phase split the 60 cycle alternating current introduced therein through the transformer 681, producing at points 682 and 683 equal A. C. voltages but displaced in time phase from each other by 90 degrees. These split voltages are impressed upon the grids 691 and 692 respectively of the amplier tube 690. Tube 690 is a self-biasing amplier whose cathodes 4693 and 693m are connected through the parallel resistancecapacitance load to ground and whose plates 695 and 696 are connected through the plate'load resistors 697 and 698 to the B+(1) supply. The two 90 degree time displaced alternating voltage phases impressed on each grid of tube 690 result in two accordingly displaced 16 sixty cycle alternating plate voltage phases on the plates of this tube, superimposed on' the D. C. plate voltage level, of which one phase is applied through the blocking condenser 677 to the grid 672 of tube 670, and the other is applied through the blocking condenser 657 to the grid 652 of tube 650. Thus, there is superimposed upon the grid potentials of tubes 650 and 670, as established by the plate 643 of tube 640, the 90 degree time displaced A. C. plate voltage phases of tube 690. Therefore, if tubes 650 and 670 are biased to a conducting level as established by the tube 640, the A. C. voltage phases impressed thereon from the above-described phase splitting circuit and amplifier cause cathodeV 676 to alternate in potential with respect to the potential of cathode 675 and cathode 656'similar1y to alternate with respect to the potential of cathode 655 in accordance with the potential alternations of grids 672 and 652, respectively. The resultant potential alternations l'are impressed upon the corresponding beam deflecting plates of the cathode ray tube 410, causing the cathode ray beam to describe substantially an annular trace on the cathode ray tube screen and causing the tracking spot to appear in the form of an annulus. This fluctuation in the potentials of the cathode ray beam dellecting plates is attained through the fact that the tubes 650 and 670, when conductive, operate as cathode followers, the cathodes thereof being connected through a large resistance to ground (see Fig. 5). Thus, the present spot returner circuit operates to dene a substantially square area upon the cathode ray tube screen outside the substantially octagonal area defined by the scoring system to delineate an on target tracking area on the cathode ray tube screen, and upon the occurrence of an error exceeding the limit so defined, the present circuit operates to change the target tracking spot into the form of an annulus to indicate an olf target condition, simulating the off target condition of an actual tracking radarscope.

Also, when tubes 650 and 670 are conductive, their circuits to points V, W, X, and Y are low impedance circuits as compared with the high impedance circuits of ampliertubes 310 and 330 to these points. As the tracking error increases, as is generally the case after tubes 650 and 670 become conductive, the first-mentioned circuits attain lower impedance values as tubes 650 and 670 become more conductive. Therefore, these low impedance circuits take over a greater and greater control of the cathode ray beam detlecting plates, thereby causing the annulus on the cathode ray tubeY screen to slowly wander back to a substantially central position in the tracking reticle and to expand in diameter as it approaches the central position, further simulating the off target condition of an actual tracking radarscope.

Control switch and conclusion The biasing voltage of the intensity grid 415 of the cathode ray tube 410, and the operation `of the signal damping portion of the feed-in bridge of the amplier 300 for simulating automatic lead angle, of the jitter generator circuit '500, ofthe spot returner circuit 600, of the scoring clock 780, and of the cam motor are all controlled by the control switch 900, illustrated in detail in Fig. 9, and there shown in operative target tracking relation to the other portions of this instrument which aer illustrated partially in detail where considered of aid in analyzing the operation of this mechanism. This control switch comprises three banks of relay operated switches, the first bank denoted by the numeral 910 comprising the relay operating coil 911 and the switch arms 912, 913, and 914, the second bank denoted by the numeral 920 comprising the relay operating coil 921 and the switch arms 922, 923, and 924, and the third bank denoted by the numeral 930 comprising the'relay operating coil 931 and the switch arms 933 and 934. ln addition, the control switch includes a manually operated 17 caging switch 940 and a micro-switch 950 mechanically controlled by a cam 151b driven by the cam motor 150.

The position of the three control switch banks shown in Fig. 9 is the operative position thereof for the normal tracking operation of the instrument. When the microswitch is closed and the caging switch is open, the coil 911 is energized and coils 921 and 931 are deenergized to position the switch banks 910, 920, and 930 in their positions shown in the drawing. As a result thereof, the scoring clock 780 is placed in a closed circuit with the 110 volt A. C. supply through points G and H under control of its relay operated switch 771, and the cam motor 150 is likewise placed in a closed circuit with this ll() volt supply. When both the micro-switch and caging switch are open, the coils 911, 921, and 931 are all deenergized to relax switch bank 91@ to its normally biased position, opposite from that shown in the drawing, and banks 920 and 930 are likewise relaxed to their normally biased positions shown in the drawing. As a result thereof, the scoring clock and cam motor are both placed in open circuits. When the micro-switch is open and the caging switch is closed, the coil 911 is `deenergized while the coils 921 and 931 are energized to relax bank 910 to its normally biased position, opposite from that shown in the drawing, and to draw banks 920 and 93S into their opposite position from that shown in the drawing. As a result thereof, the scoring clock 780 is placed in an open circuit while cam motor 150 is placed in a closed circuit to the 110 volt A. C. supply. By a consideration of the wiring diagram of Fig. 9, showing the circuit relation of the coil 911 to the micro-switch 95() and of the coils 921 and 931 to caging switch 949 and switch 912, and of the motor 150 and scoring clock 780 to the switches 914 and 924, the above-described operational control of the micro-switch and caging switch over the motor and scoring clock will be apparent.

In addition to the previously described course cams 151 and 15111 (Figs. l and 2), the cam motor 150 also operates the switch cam 1511) for controlling the microswitch. When all these cams are properly positioned on the motor shaft, the switch cam is initially positioned to leave the micro-switch open. However, upon the manual closure of the caging switch 940, the motor 150 is energized as previously indicated to drive the cams a few degrees, whereupon the switch cam closes the micro-switch. The motor is thus placed in an open circuit and further rotation of the cam is stopped until the caging switch is manually opened to again energize the motor and place the entire instrument in condition for the tracking operation, as previously explained. The switch cam is designed to hold the micro-switch closed during the remainder of the cycle of the course cams and i permit the tracking operation to proceed in its normal manner. Upon the completion of the cycle of the course cams, the switch cam again releases the micro-switch to deenergize the motor 150 and open the scoring clock circuit.

In addition to its control over the course cam motor and the scoring clock, the control switch also exerts an operational influence on other portions of the present instrument. When solenoid coil 911 is energized, switch 913 connects grid 415 of the cathode ray tube 41@ to its intensity control potentiometer 417, while deenergization of this coil enables bank 91) to relax to its normally biased position which would completely cut ot the cathode ray beam by the application of the complete B-(l) potential to this grid. Thus, the closure of microswitch 950 places the cathode ray tube in operative tracking condition. The B+(3) potential, upon which the jitter generator unit 596 operates, is connected thereto through switch 923 in the second bank 920 of the control switch which closes the circuit therebetween when in its normal operative position as shown in Fig. 9 with the coil 921' deenergized. Also, when the relay coil 921 is energized, switch 922 is closed to its contacts to ground the grids of tubes 659 and 679 through point E to eliminate the effect of the spot returner circuit 690 upon the cathode ray tube 410. The third bank 930 of the control switch, shown in Fig. 9 in its normal operative position with its coil 931 deenergized, operates through its switches 933 and 934- to connect the switch 289 in the train amplifier feed-in bridge 2410 to the resistor ZSS and to so connect the corresponding switch and resistor in the elevation portion, establishing the desired lead angle damping of variations in the output of the phase sensitive detector 2&9. When coil 931 is energized to move bank 939 to its opposite position from that shown, the switches 933 and 934i shunt and discharge the condenser 286 or 2SC? and the corresponding condenser in the elevation portion. Thus, when the control switch is in the condition shown in Fig. 9 as results from a closed micro-switch and an open caging switch, the instrument is in its normal target tracking condition with the cathode ray tube operating, the lead angle dal lping portions of the feed-in bridges for the tracking error signal amplifiers in operative condition, the cam motor energized, and the several circuits auxiliary to the tracking circuit in functioning condition. However, when both the micro-switch and caging switch are closed, relay bank 910 under control of the micro-switch remains in its position shown while banks 92@ and 931B move to their opposite positions from those shown to cage the instrument: shunting and discharging the lead angle damping condensers, deenergizing the cam motor, the scoring clock, and the jitter generator, and eliminating the eiect of the spot returner upon the tracking circuit.

if during the normal tracking of an imaginary target with the control switch in uncaged position, as shown in Fig. 9, such a large tracking error occurs as to initiate the spot returner circuit 691'), as described in a preceding section of the present specification, the cathode ray beam spot on the cathode ray tube screen immediately turns into an annular form indicating that the instrument is oit target, and the spot returner circuit takes over control of the cathode ray beam deflecting plates to a greater or lesser degree in accordance with the magnitude of tracking error. To get back on target, the caging switch 949 is manually closed to place the control switch in caged position by energizing the solenoid coils 921 and 931. rThis operation removes the effect of the spot returner circuit 606 from the tracking circuit by grounding the former at point E', to again place the cathode ray beam deflecting plates of the cathode ray tube 410 under control of the output of the amplifier 300 as carried at points M, N, O, and P, thus reestablishing the target tracking spot on the cathode ray tube screen to indicate the exact tracking error. Also, the course cam motor circuit is opened to halt the imaginary target course, the scoring clock circuit is opened, the lead angle signal damping condensers of the tracking amplilier input bridges are shunted and discharged, and the jitter generator power supply is cut oit to stabilize the tracking spot on the cathode ray tube screen. With the circuit in this condition, the trainee may readily adjust the train and elevation director rotors 112 and 132 to return the target tracking Spot to within the on target area on the cathode ray tube screen. Upon reestablishing the target tracking spot in the on target area, the manually operated caging switch 949 is opened, returning the control switch to its normal operative position shown in Fig. 9 by deenergizing the solenoid coils 921 and 931, thereby reestablishing normal operation of the instrument.

Thus, in normal operation of the present instrument an operating voltage supply such as volt A. C. is applied to the director Course unit 109, to the course cam motor 15d?, and to the control switch circuit 909, which is shown in uucaged position in Fig. 9. With the control switch in its uncaged position, the various component units of the present instrument operate and cooperate with each other in the manner described above in the Y 19 detailed'discussion of each of said componentunits., In general,` tracking errorsproduced in thev director course unit are represented by voltages: carried at points A, B, and C for train tracking error and points D, E, and F for elevation tracking error, which voltages are applied to the phase sensitive detector unit generally indicated by the numeral 200, wherein the direction of train and elevationtracking errors are established by the direction ofv potential differencey between points I andv I for train tracking error and points K and4 L for elevation tracking error. ri`he potential differences existing at these points are amplied inthe differential amplier 300 and are applied through'points M, N, O, and P to the cathode ray'beam deecting plates, 411 and 411er for train tracking error, and 412. and 412e forv elevation tracking error. The potential differences thus established onithe cathode ray beam'deecting plates causel a corresponding deflection of the cathode ray beam or theY target tracking spot on the cathode ray tube'screen, to indicate the direction and magnitude of the` combined train and elevation tracking error. The trainee attempts to follow the imaginary target course by correcting the tracking error thus indicatedthrough proper manipulation of the train and elevation director rotor control dials, or the like. Simultaneously with the above-described operation of the tracking circuit, the jitter generator 500 operates to apply a varying and vibrating potential diierence between corresponding beam deecting plates of the cathode ray tube, thus impressing a small wander motion on the target tracking spot and superimposing a jitter action upon said wander motion. Also, the scoring system 700 functions toV denne an area on the cathode ray tube screen, substantiallyv in thev form of a regular octagon aboutthe null point or Zero tracking error position of the target tracking spot. So'longas the potential at points M, N, O, and P are notlarge enough tocause the target tracking spot to pass belond thelimit so defined, the'scoring clock switch 771 remainsclosed to energize the scoring clock 780 andindicate' accurate target tracking. Inv addition, an ontarget areafis defined on the cathode ray tube screen substantially in the form of a square, detining an area extending lbeyondthat established by the scoring system. SoV long as the amplified voltages carriedl at pointsR, S, T, and-U arenotsutiicient to carry the target tracking spotI outside this on target area, the tracking circuit operates in its normal target tracking manner, although the error maybe great enough to deenergize the scoring clock; If'the trackingv error exceeds the on target area4 and the tracking vis off target, a low impedance spot returner unit 600'substantial1y takes'over control of the cathode rayl beam deilecting plates in place ofthe highfl impedance tracking circuit, causing the target tracking spot to assume the shapeof an annulus and to wander generally-toward the center of the cathode ray tube screen as theV continued action of thev course cam motor causes "the error to increase;l To reestablish' eiect of the spot returner, eliminating the tracking errorv signal 'damping portion'of the amplier input bridges 240 and 241, opening the scoring clock circuit, and deenergizing the course cam motor, thereby enablingth'e trainee, by proper manipulation of the train and elevation director rotor control dials, to reestablish an on target position of the target tracking spot onA the cathode ray tube screen. Whereupon, the caging switch 940 is'openedand tracking may be continued by the normal operation of the'instrument asdescribed above. Thus, the presentinstrument provides a simulation of the actual `conditions of radar tracking with a` train-elevation `radars'ciopeas used with gun directors and'enables the trainingof personnel'in the art ofaccurate radar tracking:

A suggested se't'of` values and type'sffor the various components ofA theseveral ntiits`- instrument are'indifcate'd the drawingsand ano 'atiife ser of' vitge snp'iie'sf thereinare" ajfrr) son vele, B+(2) 3D0 vous', BH3) 225; volts,- Bft) assigns; 13-(1)v -30() 'volts, B`(2 y -SQO'voltsgttisprese'- ing'one complete andy operative'enibodiment of the present instrument. However; it n ot intended to limit the scope of the present invention' tothe Valuesand o haracteristics thus indicated, nor I,to the preciseembodirnent herein deseribed,- but' nidications' of this invention within the spirit and scopethereof, 9S deid by ih appended claims; will be apparent tothose `skilled in the' art and are within the contemplation of the present patent.

l. A device for simulating radar tracking comprising; a director and'course uniti having a control transformerI system, means for rotating the rotor of one' generatorpt said system in accordancewith a desired'pattern to represent a target course, andl nieansfor manuallyrotting the rotor of theother generator of saidsystem'for tracking the rotational movements of the rS t-rnentioned rotor, said system producingal voltage'signal output in accordance with the noi'isyncliroiious displacement between the two rotors representing the trackingI error; a catliode ray tubeV for receiving the signal asa potential difference acr'osstwo of its beamdeil'ecfting plates; a phase sensitive detector unit'for determining vthe direction of' tracking j error by the time phasev relationship of said sigrialto the operating input voltage `o fs'aiddirector unit and applyingthe signal to said plates as to A effect beam deflection in" one direction for one. signal phase and inthe' other' direction forv they otherv signal phase," deflections of the cathoderay'bearri'spot on the cathode ray tube screenthus indicating the ilna'gnitudeafnd direction of tracking error; a jitter generator', comprising aplurality of relaxation oscillators, connected to said deecti'ngpl'ates' to impart a wander; and jitter action to cathodera'y' bear'n; an off-target in'dica'ting'funit, including a 90'degre'e phase splitting circuit connected across saidbe'a'rn deflecting plates and operating'in'response to a desiredlexcessive potential difference output of said detector unit for converting said cathode raybe'atn'spotta substantiallycir-- cular trace on'the cathode rey tube sereen;' arida' scoring system including a" relay and a timer actuated'thereby said relay acting tddeene'rgize said timerinresponse to said `signal upon the' tracking' error exceeding determined magnitudes.'

2. A devi'ce'for simulatingrad'ar' trackingconiprisingz a director and course unit havingi aj control transformer system', means vforrotating the rotor o one generator" of said system inaccordanceiw lila desired'p atterrrtoy rep'-v resent a target course, and ns for manually' rotating the rotor ofthe other generator of said systernfor' track. ing the rotational movementsofthe tirst-mcntionedrotor,

said systemprodueing'avoltage"signal output in'accfo'rddetector for'determiningI thedirec'tion of tracking error4 by the time phase relationship of said signal to the operating input'voltagefof said director unit and applying the signal to said plates'as to effect beam deilection in' one direction for onesignalphas'e and'in the other direction for the'other signal phase, dee'ctions ofthe cathode ray beam spotfon thecathode ray tube screen thus indicating the magnitude'and direction of trackin'gerror; a jitter generator comprising' a'plurality of relaxation oscillators conne'cted to' said beam deectingl plates` to impart a wander and jitter action to thec'athode ray beam.

3. Adevice'torsitnulatingradar'tracking comprising: a director and course unitlli vlng a 'control transformer system, means for" rotatingthe ro'torfot one' generator of said system in""accordance witha desired patternto' rep- 21 resent a target course, and means for manually rotating the rotor of the other generator of said system for tracking the rotational movements of the first-mentioned rotor, said system producing a voltage signal output in accordance with the nonsynchronous displacement between the two rotors representing the tracking error; a cathode ray tube for receiving the signal as a potential difference across two of its beam deecting plates; a phase sensitive detector unit for determining the direction of tracking error by the time phase relationship of said signal to the operating input voltage of said direction unit and applying the signal to said plates as to eiect beam deection in one direction for one signal phase and in the other direction for the other signal phase, deections of the cathode ray beam spot on the cathode ray tube screen thus indicating the magnitude and direction of tracking error, an amplitude detector for determining the amplitude of the output signal of said system, a time recording mechanism, and means connecting said amplitude detector to said time recording mechanism for interrupting the latter in response to signals exceeding a predetermined amplitude.

Andrews July 31, 1945 Berry Dec. 11, 1945 Bowie May 7, 1946 Busignies Nov. 26, 1946 Andrews et al. Apr. 6, 1948 Fritschi June 1, 1948 Smith et al. Aug. 31, 1948 Dehmel May 24, 1949 Salinger et al. June 7, 1949 Cesareo Dec. 27, 1949 Springer Oct. 10, 1950 Brettell et al. Mar. 13, 1951 Hales .lune 5, 1951 Decker July 3, 1951 Hisserich et al. July 29, 1952 .Tones Aug. 5, 1952 Garman et al Sept. 22, 1953 

